i'm running CorelDraw 2018 on Windows 10. There are some old files that won't open properly. Can one install an older version of CorelDraw, X4 on a pc that already has newer version?
Yes, but you must remember to run a "repair" on CD2018 after you have installed X4
I can't even install X4.
Yes, you can install both or several versions, no matter the order.
But you must remember that Windows will use by default the latest installed version. That means, if you have CorelDRAW 2018 installed, an then install X4, when you double click a CDR file, Windows will use X4. Also, the thumbnails could be the X4, so maybe some newest files file have no thumbnail. And, if you edit a bitmpa on 2018, it will start PhotoPaint X4 because Windows has the information about this. You can solve this under Control Panel / Programs, choose "repair" on 2018 in order to restore the program settings
Not sure if X4 will even run on Windows 10, haven't tried.